The Posthas launched a campaign calling for half of the £942 million a year Midland families pay in licence fees to be reinvested in this region. Presently, while the BBC reinvests roughly 50 per cent or more in every other UK region, that figure is less than nine per cent here.

Mr Johnson was in the region to support Tory candidates Julian Knight, standing in Solihull, and Rachel Maclean, contesting Northfield – both of whom support the Post campaign.

Mr Johnson agreed present spending levels, which mean just £12.40 is reinvested for every Midlands licence fee-payer, were unfair and joined calls for the broadcaster to address the imbalance. "I agree with Julian – I can't understand why this would be," he told the Post.

Mr Johnson said the Post's call for half of BBC income to be reinvested in the region where it was raised was "a good idea", adding: "I will join you in that campaign, along with Rachel Maclean, for proper BBC funding here in the Midlands."

While the Midlands contributes £942 million a year to the BBC through licence fees, only about £80 million was reinvested here last year.

The £12.40 per licence fee-payer here compares to £80 in the North, £122 in Wales and £757 in London.

Creative sector bosses say that level of investment is having a major knock-on effect on television and radio production in the Midlands.

It is also a major regional development issue as, if the BBC invested the same amount per licence fee-payer in this region as it does in the North and South, it would be an extra £400 million a year. That would generate an £800 million a year boost to the region's economy on the basis that the BBC claims that, for every £1 it spends, it generates £2 in gross value-added.

As Mayor of London, Mr Johnson is a valuable ally to the cause. He is also presently the favourite to replace David Cameron as leader of the Conservative party, after the Prime Minister last week announced that he would not serve a third term.

Mr Cameron had said it was important to "make sure the West Midlands gets a fair bang for its buck" in forthcoming debates over the BBC charter.

The BBC Trust has set a target of seeing 50 per cent of network budget spent outside London by 2016.

While it is on course to meet that target, the Midlands is the only UK region outside the capital which has seen investment decline in the past five years. The Post reported last week that Solihull candidate Mr Knight, a former senior BBC journalist, backed the campaign calling for fairer investment from the broadcaster. Lib Dem Lorely Burt, who is also contesting the seat, has already supported the cause.

Mrs Maclean, who is contesting the Northfield seat against Labour's Richard Burden, who has also campaigned for more BBC spending, said she would campaign on behalf of the region were she successful on May 7.

She said: "I think Birmingham is a centre for the creative and digital industries – I know that from my experience linking young people to businesses.

"We are very strong in this field and I think it is important that the BBC – which is nationally-funded body – recognises the role that Birmingham should play. There is a big drive with the Government now to rebalance the economy outside London and the BBC has to fall into line with that, especially as it is publicly-funded."

Mr Burden said after he had dealt with several director-generals, it was time the BBC "put its money where its mouth is."

Picture taken to mark the BBC's move from Pebble Mill to The Mailbox in 2004. From left: Bryn George, Stuart Onyeche and Craig Wood carry the corporation's logo

He added: "We will accept support from wherever it comes but the key thing is the BBC listens to the voices from the West Midlands who aren't asking for anything that isn't common sense.

"We are not asking for charity – it would make sense for the BBC to look at the Britain tomorrow – in terms of ethnicity, age and so on – and for that you look to Birmingham today."

A BBC spokesman said: "As previously stated, Birmingham is really important to us and that's why we've put a lot of effort into building up the BBC in the city over the past 12 months.

"We're investing an additional £23.5 million in Birmingham and are moving another 200 jobs there, including the globally respected BBC Academy.

"Licence fee-payers rightly expect us to operate efficiently, and it's simply not affordable to have BBC studio facilities in every part of the country.

"But BBC Birmingham remains the home of the world's most popular radio drama, The Archers, and popular BBC One shows like Doctors, Father Brown and forthcoming drama The Coroner.

"It's crucial that we produce programmes and services that reflect the whole region properly and 78 per cent of people in the West Midlands say they approve of the BBC. We're clear that BBC Birmingham will be a strong, vibrant, and sustainable base, fit for the future in a fast changing media landscape."